Hydraulic apparatus



May 30, 1961 G. A. WAHLMARK HYDRAULIC APPARATUS 2 Sheets-Sheet 1 Filed Sept. 29. 1958 May 30, 1961 M R 2,986,093

HYDRAULIC APPARATUS Filed Sept. 29, 1958 2 Sheets-Sheet 2 frzz/enZ br" Gunner Q: Ida/51mm:

United States Patent HYDRAULIC APPARATUS Gunnar A. Wahlmark, Rockford, 111., assignor to Borg- Warner Corporation, Chicago, lll., a corporation of Illinois Filed Sept. 29, 1958,'Ser. No. 763,882

2 Claims. (Cl. 103-38) This invention relates to a wobble plate hydraulic apparatus, and in particular, relates to a Wobble plate, piston-type hydraulic pump or motor having means to vary the position of the wobble plate whereby the strokes of the pistons operatively interconnected therewith may be varied between maximum throw positions and minimum throw positions.

It is well known in the art to construct a wobble plate, piston-type hydraulic apparatus, such as a hydraulic pump or motor, wherein means are provided to vary the position of the wobble plate relative to the cylinder block in order to vary the strokes of the pistons between maximum throw positions and minimum throw positions. When the hydraulic apparatus is utilized as a hydraulic pump, the amount of fluid pumped by the apparatus is varied when the position of the wobble plate is varied, and, when the hydraulic apparatus is used as a hydraulic motor, the speed of the output shaft is varied when the position of the wobble plate is varied.

Generally, the hydraulic apparatus comprises a housing having a cavity formed therein. A cylinder block having a plurality of cylinders formed in circular array therein is disposed within the housing cavity. A plurality of pistons are respectively received in the cylinders of the cylinder block and are operatively interconnected with a wobble plate pivotally mounted within the housing cavity'.

The wobble plate, being angularly disposed relative to the cylinder block, is interconnected with an input or output member which, when acting as an input member for a hydraulic pump, causes the wobble plate to wobble and thus reciprocate the pistons to pump fluid; and, when acting as an output member for a hydraulic motor, transforms the wobble motion of the wobble plate, caused by fluid pressure reciprocating the pistons, to rotary motion to thus drive a utilization device connected therewith.

Normally, the wobble plate is spring biased into engagement with an element mounted in the housing cavity, the wobble plate being adapted to wobble against the element. By selectively moving the element relative to the housing, the wobble plate being spring biased into engagement therewith is caused to pivot about its pivot axis whereby the angular relation thereof relative to the cylinder block is varied to thereby vary the strokes of the pistons. Many different means have been designed for selectively varying the position of the wobble plate in a piston-type hydraulic apparatus.

It is therefore an object of this invention to provide an improved means for varying the strokes of the pistons in a wobble plate, piston-type hydraulic apparatus.

It is another object of this invention to provide in a wobble plate, piston-type hydraulic apparatus, means for varying the position of a pivotally mounted wobble plate operatively interconnected with the pistons whereby the strokes of the pistons may be varied between maximum throw positions and minimum throw positions.

A further object of this invention is to provide an improved wobble plate, piston-type hydraulic apparatus including, a cylinder block having a plurality of cylinders Patented May 30, 1961 in the cylinder block whereby the element is adapted to be axially moved relative to the cylinder block, a plurality of pistons adapted to reciprocate respectively in the cylinders, a pivotally mounted wobble plate operatively interconnected with the pistons and adapted when pivoted to vary the strokes of the pistons and the cylinders between maximum throw positions and minimum throw positions, the wobble plate being adapted to wobble against the movable element, and means for axially moving the element relative to the cylinder block whereby the wobble plate is pivoted to thereby vary the strokes of the pistons.

Other and more particular objects, advantages, and uses of this'invention will become apparent from a reading of the following specification taken in connection with the accompanying drawings forming a part thereof and wherein:

Figure 1 illustrates, in an axial cross-sectional view, a wobble plate, piston-type hydraulic apparatus formed in accordance with the teachings of this invention.

Figure 2 illustrates, in a fragmentary cross-sectional view, certain elements of the hydraulic apparatus illustrated in Figure l and taken on line 2-2 thereof.

Figure 3 illustrates one of the elements utilized in the hydraulic apparatus illustrated in Figure 1.

Reference is now made to the accompanying drawings wherein like reference numerals and letters are used throughout the various figures to designate like parts where appropriate, and particular reference is made to Figure 1 illustrating a hydraulic apparatus, generally indicated by the reference letter A, comprising a plurality of housing sections 10 and 11 suitably fastened together in aligned relation by a plurality of bolts 12.

The housing section 10 is provided with a cavity 13 interrupting a flat end surface 14 thereof and interconnecting with a bore 15 interrupting another end surface 16 thereof. The housing section 11 is provided with a bore 17 interrupting a flat end surface 18 thereof and terminating within the housing section 11 to define a flat end wall 19. The end wall 19 of the housing section 11 is interrupted by a bore 20 which terminates within the housing section 11 to define another end wall 21.

A cylinder block 22, having a cylindrical portion 23 and an outwardly projecting flange portion 24 at one end 25 thereof, is disposed within the cavity 13 of the housing section 10 and has the flange portion 24 thereof sealably disposed between the flat surfaces 14 and 19 of the respective housing sections 10 and 11.

A valve plate 26 having a pair of opposed flat surfaces 27 and 28 is disposed within the bore 20 of the housing section 11 whereby the flat surface 27 thereof is disposed in sealing engagement with a pair of concentrically disposed seal ring means 29 and 30 carried by a plate 31 fastened to the end wall 21 of the housing section 11 by a plurality of bolts 32. The other flatsurface 28 of the valve plate 26 is disposed in sealing engagement with a flat surface 33 formed on the end 25 of the cylinder block 22.

The cylinder block 22 is provided with a plurality of cylinders 34 disposed in circular array in the cylindrical portion 23 thereof. Each cylinder 34 is adapted to receive an enlarged piston head 35 of a piston 36 having an enlarged hemispherical end portion 37 thereof disposed in a respective socket 38 formed in a wobble plate 39. The wobble plate 39 is pivotally mounted to the housing section 10 by a pair of trunnions 40 (only one being shown) formed on the wobble plate 39 and rotatably received within suitable bearing means (not shown) carried by a U-shaped or yoke member 41 which is, in

assume turn, rotatably supported on a shaft 42 secured to the housing section 10.

The wobble plate 39 is mounted on a sleeve means 43 by roller elements 44 and 45 disposed therebetween. The sleeve means 43 is provided with a bore 46 passing eccentrically therethrough which is adapted to receive a spherical portion 47 of an input or output member 48.

The input or output member 48 comprises a shaft portion 49 extending from the spherical portion 47 thereof and projecting within the bore 15 in the housing section 10. The shaft portion 49 of the input or output member 48 is rotatably supported within the bore 15 of the housing section by bearing means, indicated generally by the reference numeral 50. The shaft portion 49 of the input or output member 48 is, in turn, suitably interconnected with a shaft 51 projecting through an end cover 52 suit ably secured to the end 16 of the housing section 10 by a plurality of bolts 53. The input or output member 48 is provided with another shaft portion 54 extending in the other direction from the spherical portion 47 thereof and is adapted to be rotatably received within a bore 55 formed through the cylinder block 22. The shaft portion 55 of the input or output member 48 is provided with a shaft portion 56 extending eccentrically therefrom and being rotatably supported within a bore 57 formed in the valve plate 26 by a plurality of roller elements 58.

The housing section 11 is provided with an inlet 59 and an outlet 60 interrupting an end 61 thereof. The inlet 59 is fluidly interconnected with an annular groove 62 formed in the plate 31 by passage means 63. The outlet 60 is fluidly interconnected with another annular groove 64 formed in the housing section 11 and defined by the bore 20 and the plate 31. The outlet annular groove 64 is disposed substantially concentrically with respect to the inlet annular groove 62, the seal ring means 30 separating the grooves 62 and 64 from each other.

The valve plate 26 is provided with an annular groove 65 interrupting the flat surface 28 thereof. The annular groove 65 is fluidly interconnected with the other flat surface 27 of the valve plate 26 by a plurality of ports 66 formed in the valve plate 26, the ports 66 being in fluid communication with the inlet annular groove 62.

As shown in Figure 3, the cylinder block 22 is provided with a plurality of angularly disposed grooves or keyway means 67 in the cylindrical portion 23 thereof. A hollow tubular element 68 is adapted to be telescopically disposed about the cylindrical portion 23 of the cylinder block 22 and is adapted to be axially and rotatably moved relative thereto in the following manner. The tubular element 68 is provided with an enlarged cylindrical portion 69 projecting radially outwardly therefrom. A plurality of angularly disposed slots 70 are formed in the cylindrical portion 69 of the tubular element 68. A pin 71 spans each slot 70 in the tubular element 68. A roller means 72 is rotatably mounted in each pin 71 and has an enlarged central wheel portion 73 adapted to be received within one of the slots 67 formed in the cylindrical portion 23 of the cylinder block 22. Therefore, it can be seen, that upon rotation of the tubular element 68 relative to the cylinder block 22, as shown in Figure l, the roller means 72 of tubular element 68 will roll within the grooves 67 and thus cause the tubular element to be rotated relative to the cylindrical portion 23 of the cylinder block 22 and also be moved axially relative to the cylinder block 22. The roller means 72 reduce the friction encountered between the tubular element 68 and the cylinder block 22 when relative movement is effected.

It is to be understood that the cylinder block 22 could carry the roller means 72 and the tubular element 68 could be provided with the angularly disposed grooves or keyway means 67 whereby the tubular element 68 is adapted to be axially and rotatably moved relative to the cylinder block 22.

When the tubular element 68 is in its extre e f position, as shown in bold lines in Figure l of the drawings,- the wobble plate 39 has an end surface 74 thereof adapted to wobble in engagement with an end surface 75 of the cylinder block 22. When the wobble plate 39 is wobbling in engagement with the end 75 of the cylinder block 22, it can be seen that the angular rela tion of the wobble plate 39 relative to the cylinder block 22 provides maximum throw of the pistons 36 within the respective cylinders 34. The wobble plate 39 is maintained in this pivoted position, whereby the surface 74 thereof is in engagement with the surface 75 of the cylinder block 22, by suitable compression spring means 76 disposed between the input or output member 48 and a flange portion 77 of the bearing sleeve 43. The spring 76 engages the input or output member 48 at one end 78 thereof and engages a cradle-like member 79 at another end 80 thereof. The cradle-like member 79 has a socket 81 receiving an end 82 of a pin 83 having another end 84 thereof disposed in a socket 85 formed in the flange portion 77 of the bearing sleeve 43.

When the tubular element 68 is moved to the right. as viewed in the drawings, an end 86 thereof is adapted to engage the surface 74 of the wobble plate 39 and thereby cause the wobble plate 39 to pivot about the pivot points 40 in opposition to the force of the spring means 76. When the element 68 has been axially moved to its extreme right position relative to the cylinder block 22, as shown in dotted lines in Figure l, the wobble plate 39 will be pivoted to a position, as shown in dotted lines in Figure 1, whereby the throw of the pistons 36 within the respective cylinders 34 is negligible.

The operation of the hydraulic apparatus A, as far as described, is as follows. Assuming that the element 68 is in the extreme left position, and the hydraulic appa ratus A is operating as a hydraulic pump, it being understood that a hydraulic pump and a hydraulic motor operate in substantially the same manner, the shaft 51 is rotated by a suitable power source (not shown) whereby the input member 48 is rotated. Upon rotation of the input member 48, the wobble plate 39 mounted thereon is caused to wobble about the surface 75 of the cylinder block 22. Because of the angular relation between the wobble plate 39 and the cylinder block 22, the pistons 36 operatively interconnected with the wobble plate 39 are caused to reciprocate within the respective cylinders 34 with strokes of maximum throw. Certain of the pistons 36 are beginning to be reciprocated to the right within the respective cylinders 34 as the input member 48 rotates thereby providing intake strokes thereof. Since the valve plate 26 is mounted on the eccentrically disposed shaft portion 56 of the input member 48, those cylinders 34 in the intake position are placed in fluid communication with the inlet groove 65 formed in the valve plate 26 whereby fluid from the inlet 59 is adapted to be drawn into the cylinders 34. When those cylinders 34 have been completely filled with fluid by the respective pistons 36 moving to the right, the pistons 36 are then moved to the left by the wobble plate 39 whereby the fluid within the respective cylinders 34 is pressurized and forced out into the outlet annular groove 64 formed in the housing section 11.

When it is desired to vary the fluid displacement of the hydraulic apparatus A, the tubular element 68 is adapted to be moved relative to the cylinder block 22 by any suitable means. When the tubular element 68 is moved to the right, the end 86 thereof engages the wobble plate 39 and causes the wobble plate 39 to pivot about its pivot points 40 thereby decreasing the angular relation thereof with respect to the cylinder block 22 and thus decreasing the throw of the pistons 36 within the respective cylinders 34. When the wobble plate 39 has been pivoted to the position shown in dotted lines in Figure l, the strokes of the pistons 36 is reduced to minimum throw, and, therefore, no fluid pressure is delivered to the outlet 60. When the tubular element 68 is axially moved to any intermediate position, the strokes of the pistons 36 are between minimum and maximum throw positions whereby. the displacement of the hydraulic apparatus A is between the minimum and maximum thereof. When the tubular element rs axially moved from the position shown in bold lines in Figure 1, the wobble plate 39 is adapted to wobble against the end 86 of the tubular element 68.

As previously stated, many different means can be provided to cause rotatable and axial movement of the tubular element 68 to thereby vary the position of the wobble plate 39 and thus vary the strokes of the pistons 36. One such means is shown in Figure 2 and comprises a piston 87 received within a cylinder 88 formed in a housing portion 89 suitably secured to thehousmg section by a plurality of bolts 90. The prston 87 has an elongated shaft 91 projecting therefrom and engaging a lip or socket portion 92 formed on thetubular element 68. Outlet fluid pressure of the hydraulrc apparatus A is conveyed to the cylinder 88 by means of a passage 93 formed in the housing 89. The passage 93 fluidly interconnects with a bore 94 formed in the housing portion 89. A valve piston 95 rs d1sposed wrtlnn the bore 94 and is biased to a closed position by a spring 96 having an end 97 thereof engaging a retainer 98 received on an adjusting screw 99 carried by a land portion 100 of the housing portion 89. Another end 101 of the spring 96 engages a cradle-like member 102 engaging a pin 103 disposed between the cradle-like member 102 and the valve piston 95.

In this manner, the output fluid pressure of the hydraulic apparatus A is conveyed through the passage means 93 to the bore 94. The force of the fluid pressure within the bore 94 acts against an end surface 104 of the valve piston 95 and tends to move the valve piston 95 in opposition to the force of the spring 96. The particular compression force of the spring 96 is selected by ad usting the position of the retainer 98 on the ad usting screw 99 in any manner well known in the art. When the force of the fluid within the bore 94 acting against the end surface 104 of the valve piston 95 exceeds the force of the sprrng 96, the valve piston 95 is moved thereby to permrt fluid communication between the bore 94 and a passage means 105, the passage means 105 being fluidly interconnected with the cylinder 88. The force of the flllld pressure conveyed to the cylinder 88 causes axial movement of the piston 87 within the cylinder 88. Upon movement of the piston 87 relative to the housing section 89, the shaft 91 thereof causes the tubular element 68 to be rotated relative to the cylinder block 22. Upon rotation of the tubular element 68 relative to the cylinder block 22, the roller means 72 carried thereby roll within the respective grooves 67 formed in the cylindrical portion 23 of the cylinder block 22 and cause the tubular element 68 to move rotatably and axially relative to the cylrnder block 22. In this manner, the strokes of the pistons 36 may be varied, as the tubular element 68 moving to the right, as shown in Figure 1, causes the wobble plate 39 to pivot about its pivot points 40 in the manner previously described.

By selecting the particular compression force of the spring 96, it can be seen that the pressure value of the fluid pressure delivered by the hydraulic apparatus A, when operating as a hydraulic pump, can be prevented from exceeding a predetermined pressure value. Assuming that the wobble plate 39 is in some intermediate position relative to the cylinder block 22 and the pressure value of the fluid pressure within the outlet 60 falls below the predetermined pressure value, the spring 96 will cause the valve piston 95 to close thereby venting the fluid pressure within the cylinder 88 back to the inlet 59 by placing a passage 106 in fluid communication with the passage 105 leading to the cylinder 88. The compression force of the spring 76 carried by the input or output member 48 is suflicient to overcome the friction of the piston 87 and the friction between the tubular element 68 and the cylinder block 22 and thereby causes the wobble plate 39 to pivot clockwise as shown in Figure 1.v The wobble plate 39 causes clockwise rotation of the tubular element 68 and thus movement thereof to the left as the flat surface 74 of the wobble plate 39 pushes against the end 86 of the tubular element 68. Clockwise rotation of the wobble plate 39 increases the strokes of the pistons 36 and thus increases the displacement of the hydraulic apparatus A.

It is to be understood, of course, that the valve piston is adapted to assume any intermediate position under the effects of the fluid pressure in the bore 94 and the force of the spring 96 whereby fluid pressure may be throttled into the cylinder 88 to thereby maintain the wobble plate 39 in any intermediate position so long as the hydraulic apparatus A is supplying fluid pressure to the outlet 60 at the predetermined pressure value.

When the hydraulic apparatus A is operating as a fluid motor, fluid under pressure is delivered to either the inlet 59 or outlet 60 depending upon the desired direction of rotation of the shaft 51. Assuming that hydraulic fluid is being delivered into the inlet 59, the force of the fluid pressure entering the cylinders 34 in communication with the inlet groove 65 in the valve plate 26 will cause the respective pistons 36 to move to the right and thereby cause the wobble plate 39 to wobble. The wobbling motion of the wobble plate 39 is transformed to rotary motion by the bearing sleeve 43 to thereby cause rotation of the output member 48 which, in turn, causes rotation of the output shaft 51. The speed of rotation of the shaft 51 may be maintained substantially constant, assuming that the load thereon remains constant, by the valve piston 95 arrangement controlling the position of the tubular element 68 relative to the cylinder block 22 in substantially the same manner previously described. It should be understood that in order to rotate the shaft 51 at a constant speed a predetermined pressure value of the fluid must be delivered to the cylinders 34 for a particular angular position of the wobble plate 39 relative to the cylinder block 22. If the pressure value varies from the predetermined pressure value, the tubular element 68 is caused to move axially relative to the cylinder block 22 to thereby vary the angular position of the wobble plate 39 and thus vary the strokes of the pistons 36. In this manner the angular position of the wobble plate 39 relative to the cylinder block 22 is varied in accordance with the variations in the pressure value of the fluid pressure supplied to the hydraulic apparatus A whereby the speed of rotation of the shaft 51 is maintained at a particular predetermined speed.

Therefore, it can be seen that there has been described a wobble plate, piston-type hydraulic apparatus having improved means for varying the angular position of the wobble plate relative to the cylinder block whereby the strokes of the pistons are varied.

While this invention has been disclosed in connection with a specific embodiment thereof, it is to be understood that this was by way of example rather than limitation, and it is intended that the invention be defined by the appended claims.

What is claimed is:

1. In a wobble plate hydraulic apparatus comprising a substantially cylindrical stationary cylinder block having a plurality of cylinders disposed therein and adapted to receive fluid, a plurality of pistons in said cylinders and adapted to be reciprocated therein, a pivotally mounted wobble plate operatively interconnected with said pistons and adapted when pivoted to vary the strokes of said pistons in said cylinders between maximum throw positions and minimum throw positions; the improvement comprising means for adjusting said wobble plate to determine the length of the strokes of said pistons to thereby vary the rate of discharge of fluid from said apparatus, said adjusting means comprising a hollow tubular element telescopically disposed about said stationary cylinder block and axially and rotatably movable relative thereto, said tubular element being adapted to engage s'aid wobble plate, means defining a plurality of angularly inclined keyways on the periphery of said cylinder block, a plurality of rollers carried by said tubular element and respectively received in said inclined keyways 5 whereby rotation of said tubular element with respect to said stationary cylinder block moves said element axially with respect thereto to adjust the wobble plate, and piston means responsive to the force of said fluid in said cylinders for rotating said tubular element.

8 A wobble plate hydraulic apparatus as defined in 'claim 1 and including compression spring means urging said wobble plate into engagement with said tubular element.

References Cited in the file of this patent UNITED STATES PATENTS McIntyre Dec. 24, 1940 Wahlrnark Apr. 28, 1942 

